Transformer with relatively movable sections

ABSTRACT

A transformer for use in feeding electrical power to rotatable or linearly movable devices, for example cranes. The transformer has a core of magnetic material made up of two relatively movable sections, a primary winding being provided on one section and a secondary winding on the other. In use, one core section is stationary and the other is secured relative to the movable device. Movement of the device is accompanied by a predetermined movement of one core section relative to the other and in each of the relative positions assumed by the sections they provide a low reluctance magnetic path for flux generated by an alternating current in one winding to link with the other winding.

' United States Patent 1 91 Bridewell et al.

[ 1 TRANSFORMER WITH RELATIVELY MOVABLE SECTIONS [75] Inventors: Alan R. Bridewell; George F. Eames,

both of Mile Cross, England [73] Assignee: Eastern Electronics (Norwich) Limited, Norwich, England [22] Filed: Nov. 30, 1973 [21] Appl. No.: 420,629

[] Foreign Application Priority Data Nov. 18, 1975 Primary Examiner-Thomas J Kozma Attorney, Agent, or Firm-Browdy and Neimark [5 7] ABSTRACT A transformer for use in feeding electrical power to rotatable or linearly movable devices, for example Nov. 30, 1972 United Kingdom 55384/72 cranes- The transformer has a Core of magnetic material made up of two relatively movable sections, a pri- 52 US. Cl. 336/; 336/96; 336/117; y winding being provided on one Seetien and e 33 120; 33 13 5 secondary winding on the other. in use, one core sec- [51] Int. Cl. H01F 21/02 tion is Stationary and the other is Secured relative to 58 Field of Search 336/119, 120, 135, 117, the movable deviee- Movement of the deviee is 33 /1 1 132 134 90 9 companied by a predetermined movement of one core section relative to the other and in each of the relative [56] References Ci positions assumed by the sections they provide a low UNITED STATES PATENTS reluctance magnetic path for flux generated by an alternating current in one winding to link with the other 1,505,325 8/1924 Elbert 336/119 X Windin 2,585,050 2/1952 Simon 2,894,231 7/1959 Krasno 336/120 X 8 Claims, 5 Drawing Figures 47 3 7 7 5 L l /l //w A 5 'A 35 3 2 8 9 b \g j g 33- Q g If I [r- I 27 K; 3 Z8 45 -k 2/ i, 3

l3' r\g. ]8

U.S. Patent Nov. 18,1975 Sheet20f3 3,921,114'

US. Patent Nov. 18, 1975 Sheet 3 of3 3,921,114

prising primary and secondary windings and a core of magnetic material, wherein the core comprises two relatively movable sections, the primary and secondary windings are provided on respective sections of the core, the core sections are supported in a manner which allows a predetermined movement of one section relative to the other, and the sections are adapted, in each position assumed by one winding relative to the other during the said relative movement, to provide a low reluctance magnetic path for magnetic flux generated by an alternating current flowing in one winding to link the other winding and to cause an electromotive force to be induced in that other winding.

The core sections may be supported in a manner which allows rotation of one section relative to the other. In this case, one core section may comprise a generally ring-shaped outer part, a central part which is disposed coaxially of the outer part, and a further part extending between the central and outer parts, and the other core section may comprise a part extending between the central and outer parts of the said one section, the two sections being rotatable relative to one another about the common axis of the central and outer parts of the said one section. The further part in the said one section may then be a generally U-shaped part and the other core section may also be generally U- shaped. Alternatively the further part in the said one core section may be generally E-shaped, extending between the said central and outer parts at diametrically opposite locations, and the other core section may also be generally E-shaped and extends between the said central and outer parts at diametrically opposite locations. Alternatively, the further part in the said one core section may extend angularly through 360 about the common axis, and the other core section may also extend angularly through 360 about the common axis.

The core sections may be supported in a manner which allows linear movement of one section relative to the other. In this case, one core section may comprise two parallel rail parts and a further part extending between the two rail parts, and the other core section may comprise a part extending between the two rail parts. Alternatively, one core section may comprise three parallel rail parts and a generally E-shaped part extending between the central rail part and each outer rail part, and the other core section may comprise a generally E-shaped part extending between the central rail part and each outer rail part.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an axial section of a first transformer ac-' FIG. 3 is a diagrammatic plan view of a second transformer according to the invention;

FIG. 4 is a perspective view, partly in section, of a third transformer according to the invention; and

FIG. 5 is a diagrammatic plan view of a fourth transformer according to the invention.

The transformer shown in FIGS. 1 and 2 of the drawings is used in feeding electrical power to rotatable devices, such as rotatable cranes. The transformer is particularly suitable for use with cranes operating in environments such as those occurring on oil rigs, where there are dangerous atmospheres, presenting a high explosion and fire risk if conventional slip rings and brushes are used.

In the transformer of FIGS. 1 and 2 a core 1 of magnetic material is made up of a stationary section 3 and a rotary section 5. A primary winding 7 is wound on the stationary core section 3 and, in use, is supplied with electrical current from an alternating current supply (not shown). A secondary winding 9 is wound on the rotary section 5 and, in use, is connected to electrical circuits on the rotary crane (also not shown). The core sections 3 and 5 together provide a low reluctance magnetic path whereby flux generated by an alternating current supplied to the primary winding 7 links the secondary winding 9 in all positions which the section 5 assumes relative to the section 3.

For housing the primary and secondary windings 7 and 9, respectively, and the rotary and stationary core sections 5 and 3, respectively, the present transformer is provided with a generally cylindrical metal casing 11. The casing 11 is made up of a lower part 13, which houses the stationary core section 3 and the primary winding 7, and an upper part 15 which is rotatably supported on the lower part 13 and houses the rotary core section 5 and the secondary winding 9.

In the lower part 13 of the casing 11 an E-shaped magnetic yoke 17, which forms part of the stationary core section 3, is arranged with a main body 18 of the yoke extending horizontally across the bottom of the casing and with two outer limbs 19 and a central limb 21 thereof upstanding from the main body. The primary winding is wound on the central limb 21 of the yoke 17. Above the yoke 17 are two further parts of the stationary core section 3. First, a ring-shaped part 23 which is arranged coaxially of the casing 11 and rests at diametrically opposed locations thereon on the outer limbs 19 of the yoke 17. Secondly, there is a generally cylindrical part 25 which rests on the central limb 21 of the yoke 17. Each of these parts 23 and 25 is formed by winding a flat strip of magnetic material into the appropriate shape, thereby providing a low reluctance path for magnetic flux in a direction along the length or across the width of the strip.

The stationary core section 3 is so dimensioned that the upper faces of the ring-shaped part 23 and the cylindrical part 25 are disposed in a horizontal plane a short distance below the top of the lower part 13 of the casing 11. At this level an increase in the internal diameter of the casing provides a lower, internal shoulder 27 and a short distance above the lower shoulder 27 there is a further increase in diameter to form an upper shoulder 29. A bearing plate 31 for supporting the upper part 15 of the casing 11 is provided on the lower shoulder 27 and the upper shoulder 29 supports a sealing ring 33, as hereinafter described.

In the upper part 15 of the transformer casing 11 the rotary section 5 of the magnetic core 1 is formed of an E-shaped yoke 35 of magnetic material. This yoke 35 is arranged with a main body 37 thereof extending diametrically across the top of the casing 11 and with outer limbs 39 and central limb 41 extending downwardly with their lower end faces in the same horizontal plane as the lower end of the part 15. The secondary winding 9 is wound on the central limb 41 of the yoke 35.

For mounting purposes the upper part 15 of the casing is formed with an external flange 43 at a location a short distance above its lower end.

In both the lower part 13 and the upper part 15 of the casing 11 the space between the casing and the associated winding 7m 9 and core section 3 or is filled with a fire retardent compound 45 such as an epoxy resin with a tri-hydrolysed alumina filler. Each part 13 and of the casing 11 is also provided with a terminal chamber 47 through which electrical connection is made to the transformer winding within that part.

In their assembled positions the upper part 15 and the lower part 13 of the casing are coaxially arranged with the undersurface of the external flange 43 on the part 15 resting on the bearing plate 31 in the lower part 13. A narrow space remains between the lower end faces of the limbs 39 and 41 of the yoke 35 and the upper faces of the ring-shaped core part 23 and cylindrical core part and this space is filled with a lubricating compound 49. The afore-mentioned sealing ring 33, which rests on the upper shoulder 29 excludes moisture and dirt from the bearing plate 31. A clamping ring 51 secures the upper part 15 of the casing 11 relative to the lower part 13 in a manner which prevents relative movement in an axial direction whilst allowing rotation of the upper part relative to the lower part.

In use, the lower part 13 of the casing 11 is secured to the ground or to a fixed support for the crane and the upper part 15 is connected to the rotary crane, preferably by a torque arm system to reduce the stresses in the bearing surfaces. The axis of rotation is coaxial with the axis of the casing 11. An alternating current supply is connected to the primary winding 7 of the transformer via the terminal chamber 47 in the lower part 13 of the casing and the secondary winding 9 in the upper part 15 is connected to electrical circuits on the crane.

For all angular positions of the crane the upper and lower core sections 5 and 3, respectively, together provide a low reluctance magnetic path for flux which extends between the primary and secondary windings 7 and 9 respectively. The path is formed of two parallel branches. One branch extends between the primary winding 7 and the secondary winding 9. via the central limb 21, the body 18 and an outer limb 19 of the lower yoke 17, a section of the ring-shaped core part 23, the narrow compound 49, an outer limb 39, the body '37 and the central limb 41 of the upper yoke 35 and, finally, across the compound 49 and back through the generally cylindrical core part 25 to the central limb 21 of the lower yoke 17. The other branch extends between the primary winding 7 and the secondary winding 9 via the'other outer limb 19 of the lower yoke, the other outer limb 39 of the upper yoke and alternative sections of the ring-shaped core part 23. The aforedescribed method of making the ring-shaped core part 23 and the cylindrical core part 25 ensures that they offer low reluctance to flux generated by an alternating current applied to the primary winding 7 and extending along each branch of the path. This is true for all angular positions of the crane, since rotary movement of the upper part 15 of the casing 11 merely increases the lengths of the ring-shaped core part 23 in each branch of the magnetic path without adding significantly to the reluctance of the path. Accordingly, there is a strong magnetic coupling-between the primary and secondary windings 7 and 9, respectively, for all angular positions of the crane and the application of an alternating current to the primary winding 7 causes a current to be induced in the secondary winding 9 with low power loss.

For efficient operation the ring-shaped core part 23 and the cylindrical core part 25 include some means of preventing or reducing circulating currents within them, without detriment to the magnetic circuit. This is achieved by cutting a very narrow slot (not shown) through the ring-shaped part 23 and a similar slot half way through the cylindrical part 25. The fixed E- shaped yoke 17 is positioned so that both the slots are bridged by the face of one outer limb 19 and by half of the face of the centre limb 21, the slots in this way have no detrimental effect on the magnetic circuit.

Referring now to FIG. 3, second rotary transformer according to the invention has a stationary core section which includes a ringshaped part 51 and a generally cylindrical part 53 constructed and arranged in the manner described above. In the present transformer, however, there are upper and lower yokes 55 and 57, respectively, which are U-shaped. Each U-shaped yoke 55 and 57 extends between the ringshaped core part 51 and the cylindrical core part 53 and has an associated primary winding 61 or secondary winding 59 on the body of the U. The U-shaped yoke 55 which forms the rotary core section is mounted for rotation about the axis of the cylindrical core part 53, which extends along one limb of the yoke 55.

As in the case of the rotary transformer of FIGS. 1 and 2, a low reluctance magnetic path is provided for flux in all angular positions of the rotary yoke 55 relative to the stationary yoke 57 and core parts 51 and 53.

A third transformer, shown in FIG. 4, is one which is suitable for use in feeding power to a linearly movable device, such as a crane which is movable alongside a quay.

In this third transformer a stationary core section is formed of an E-shaped yoke 71 and three rails 73. The rails 73 are disposed in a horizontal plane and extend parallel with one another along the direction of movement of the crane. The yoke 71 is arranged below the rails 73 with the body of the E extending transversely of the rails and the limbs upstanding so that the upper end faces thereof contact respective rails. A movable core section of the transformer is formed of an E- shaped yoke 75 which is arranged above the rails 73 with the body of the E extending transversely of the rails and the limbs extending downwardly so that their lower end faces are spaced at short distance above respective rails.

A primary winding 77 is provided on the central limb of the stationary yoke 7 1 and secondary winding 79 on the central limb of the movable yoke 75.

In use, the stationary core section is mounted on the quay with the rails 73 extending parallel with the direction of movement of the crane. The movable core section is secured relative to the crane. An alternating current supply is connected to the primary winding 77 and electrical circuits on the crane are connected to the secondary winding 79.

As in the transformers described above, there is again a low reluctance magnetic path for flux extending between the primary winding 77 and secondary winding 79 for each position assumed by the movable core section as it is moved relative to the stationary core section. The path is formed of two branches, each extending between the primary winding 77 and secondary winding 79 via the central limb, the body and an outer limb of the stationary yoke 71, an outer rail 73, an outer limb, the body and the central limb of the movable yoke 75, and finally back acrossthe central rail 73 to the central limb on the stationary yoke 71.

Referring to FIG. 5, a fourth transformer according to the invention is also used in feeding power to a linearly movable device. This transformer bears a similar relation to the third transformer described above as does the second to the first. Thus, the present transformer has a stationary core section made up of two parallel rails 81 bridged by a U-shaped yoke 83 and a movable core section made up of a further U-shaped yoke 85. A primary winding 87 is provided on the body of the stationary yoke 83 and a secondary winding 89 is provided on the body of the movable yoke 85.

We claim:

1. A transformer comprising:

a core of magnetic material consisting of first and second U-shaped sections which are rotatable relative to one another about an axis of the core;

a primary winding provided on one of said core sections;

a secondary winding provided on the other of said core sections; and

a ring-shaped section of magnetic material at the outer part of said core, the axis of said ring-shaped section lying along the axis of said core;

wherein each of said first and second U-shaped sections comprises a first limb extending along the axis of the core, a body which extends radially outwardly from the first limb, and a second limb which extends in an axial direction from an outer end of said body to the ring-shaped section;

whereby the core can provide, in each position assumed by one core section relative to the other during rotation about said axis, a low reluctance magnetic flux generated by an alternating current flowing in one winding to link the other winding and to cause an electromotive force to be induced in that other winding.

2. A transformer according to claim 1, wherein said ring-shaped section is a flat strip of magnetic material wound into the shape of a ring.

3. A transformer according to claim 1, wherein said ring-shaped section is formed with a narrow slit to reduce circulating electric currents therein.

4. A transformer according to claim 1, further comprising a generally cylindrical metal casing formed of two parts which are mounted for rotation relative to one another about the axis of the casing, said casing enabling said transformer to be used in explosive atmospheres.

5. A transformer comprising:

a core of magnetic material consisting of first and second E-shaped sections which are rotatable relative to one another about an axis of the core;

a primary winding provided on one of said core sections;

a secondary winding provided on the other of said core sections; and

a ring shaped section of magnetic material at the outer part of said core, the axis of said ring-shaped sector lying along the axis of said core;

wherein each of said first and second E-shaped sections comprises a first limb extending along the axis of the core, a first body portion which extends radially outwardly from the first limb, a second limb which extends in an axial direction from the outer end of said first body portion to the ring-shaped section, a second body portion which extends radially outwardly from said first limb along the longitudinal axis of the first body portion away from said second limb, and a third limb extending in an axial direction from the outer end of said second body portion opposite said second limb. said second and third limbs extending toward diametrically opposite locations on said ring-shaped section.

6. A transformer according to claim 5, wherein said ring-shaped section is a flat strip of magnetic material wound into the shape of a ring.

7. A transformer according to claim 5, wherein said ring-shaped section is formed with a narrow slit to reduce circulating electric currents therein.

8. A transformer according to claim 5, further comprising a generally cylindrical metal casing formed of two parts which are mounted for rotation relative to one another about the axis of the casing, said casing enabling said transformer to be used in explosive atmospheres. 

1. A transformer comprising: a core of magnetic material consisting of first and second Ushaped sections which are rotatable relative to one another about an axis of the core; a primary winding provided on one of said core sections; a secondary winding provided on the other of said core sections; and a ring-shaped section of magnetic material at the outer part of said core, the axis of said ring-shaped section lying along the axis of said core; wherein each of said first and second U-shaped sections comprises a first limb extending along the axis of the core, a body which extends radially outwardly from the first limb, and a second limb which extends in an axial direction from an outer end of said body to the ring-shaped section; whereby the core can provide, in each position assumed by one core section relative to the other during rotation about said axis, a low reluctance magnetic flux generated by an alternating current flowing in one winding to link the other winding and to cause an electromotive force to be induced in that other winding.
 2. A transformer according to claim 1, wherein said ring-shaped section is a flat strip of magnetic material wound into the shape of a ring.
 3. A transformer according to claim 1, wherein said ring-shaped section is formed with a narrow slit to reduce circulating electric currents therein.
 4. A transformer according to claim 1, further comprising a generally cylindrical metal casing formed of two parts which are mounted for rotation relative to one another about the axis of the casing, said casing enabling said transformer to be used in explosive atmospheres.
 5. A transformer comprising: a core of magnetic material consisting of first and second E-shaped sections which are rotatable relative to one another about an axis of the core; a primary winding provided on one of said core sections; a secondary winding provided on the other of said core sections; and a ring shaped section of magnetic material at the outer part of said core, the axis of said ring-shaped sector lying along the axis of said core; wherein each of said first and second E-shaped sections comprises a first limb extending along the axis of the core, a first body portion which extends radially outwardly from the first limb, a second limb which extends in an axial direction from the outer end of said first body portion to the ring-shaped section, a second body portion which extends radially outwardly from said first limb along the longitudinal axis of the first body portion away from said second limb, and a third limb extending in an axial direction from the outer end of said second body portion opposite said second limb, said second and third limbs extending toward diametrically opposite locations on said ring-shaped section.
 6. A transformer according to claim 5, wherein said ring-shaped section is a flat strip of magnetic material wound into the shape of a ring.
 7. A transformer according to claim 5, wherein said ring-shaped section is formed with a narrow slit to reduce circulating electric currents therein.
 8. A transformer according to claim 5, further comprising a generally cylindrical metal casing formed of two parts which are mounted for rotation relative to one another about the axis of the casing, said casing enabling said transformer to be used in explosive atmospheres. 